Role of neuronal migration genes in synaptogenesis and plasticity

描述(申请人提供)：脊柱和突触密度在临床材料以及自闭症和精神分裂症的动物模型中都是异常的，包括携带脆性X智力低下蛋白(FMRP)和Rett基因MeCP2突变的小鼠。心理健康研究的一个主要焦点是确定大脑发育过程中突触形成和持续的调节机制。目前关于自闭症行为的假说不仅包括有缺陷的突触接触的形成，而且还包括一旦形成突触就没有成功地修剪突触，或者在儿童发展过程中没有建立新的联系。丝状足最有可能是树突棘的前身，树突棘是大多数突触的位置，两者都依赖于它们的运动性来采样、测试并最终形成接触和突触，以形成适当的回路。虽然许多树突刺在一生中都被维持着，但许多刺被消除了，新的刺形成了，可能反映了失去的记忆或新的接触，从而获得了记忆。虽然有强有力的迹象表明它的潜在重要性，但它在信号转导和迁移后神经元运动中的作用基本上是一个未知的研究领域。我们的实验室先前已经证明，Lis1显著影响小GTP酶RhoA、rac1和CDC42的调节，Lis1单倍体缺陷损害了这些Rho家族GTP酶对NMDA受体介导的钙内流的激活，这与Lis1的信号转导作用是一致的。此外，Lis1单倍体功能不全与海马神经元和小脑神经元突起上丝状足突的形成显著减少有关。我们建议证明Lis1在树突状丝状足和棘突的形成以及转化为突触形成和稳定性的运动性中起着重要的作用。这将进一步阐明Lis1作为突触发生和可塑性的重要分子的新作用。我们将研究Lis1水平与树突状丝状足细胞和棘细胞运动的相关性。利用旋转圆盘共聚焦成像和双光子成像，我们将分别在体外和体内系统中分析丝状足和棘突的发育和形态。最后，我们将进行实验，通过分析已知的Lis1相互作用因子，包括裸异构体裸体类1(NDEL1)和NDEL1相互作用蛋白DISC1，重点了解控制这些事件的分子机制。Lis1可能在外部信号和细胞骨架调节之间提供了一个关键的联系，从而支持了活性依赖的突触可塑性。

DESCRIPTION (provided by applicant): Spine and synapse density are abnormal in clinical material and in animal models of autism and schizophrenia, including in mice bearing mutations in the fragile-X mental retardation protein (FMRP) and the Rett gene, MeCP2. A major focus in mental health research is defining the mechanisms regulating formation and persistence of synapses in developing brain. Current hypotheses regarding autistic behaviors include not only formation of faulty synaptic contacts but also failure to successfully prune synapses once formed or make new connections during childhood development. Filopodia are the most likely predecessor of dendritic spines, the sites of most synapses, and both rely on their motility in order to sample, test and finally make contacts and synapses to form proper circuits. While a lot of dendritic spines are maintained throughout life, many spines are eliminated and new spines are formed that could reflect memories lost or new contacts, and thus memories, gained. While there are strong indications of its potential importance, the role of Lis1 in signal transduction and post-migration neuronal motility is an essentially uncharted area of investigation. Our laboratory has previously shown that Lis1 significantly influences the regulation of small GTPases RhoA, Rac1 and Cdc42, that Lis1 happloinsufficiency impairs the activation of these Rho-family GTPases upon NMDA-receptor mediated calcium influx, and that is consistent with a signal transduction role for Lis1. Moreover, Lis1 happloinsufficiency is associated with marked reduction in filopodia formation on neurites of hippocampal and cerebellar neurons. We propose to demonstrate that Lis1 plays a prominent role in dendritic filopodia and spine formation and motility that translates into synapse formation and stability. This will further elucidate a new role of Lis1, as a molecule important for synaptogenesis and plasticity. We will investigate the dependence of Lis1 levels on the motility of dendritic filopodia and spines. Using spining-disc confocal and two-photon imaging, we will analyze development and morphology of both filopodia and spines in in vitro and in vivo systems, respectively. Finally, we will conduct experiments that will focus on understanding molecular mechanisms governing these events by analyzing known Lis1 interactors, including the nudE isoform NudE-like 1 (NDEL1) and NDEL1 interacting protein DISC1. Lis1 may provide a critical link between external cues and cytoskeletal modulation underpinning activity-dependent synaptic plasticity.